Shortwave infrared optical imaging through an electronic device display

ABSTRACT

Systems and methods for through-display imaging. An optical imaging sensor is positioned at least partially behind a display and is configured to emit shortwave infrared light at least partially through the display to illuminate an object, such as a fingerprint, in contact with an outer surface of the display. Surface reflections from the object are received and an image of the object can be assembled.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/143,390, filed Sep. 26, 2018, the contents of which are incorporatedherein by reference as if fully disclosed herein.

FIELD

Embodiments described herein relate to electronic device displays and,in particular, to display stack constructions facilitatingthrough-display shortwave infrared biometric imaging.

BACKGROUND

An electronic device display (a “display”) is typically formed from astack of functional and structural layers (a “display stack”) that isattached to, or otherwise disposed below, a protective cover. In manyconventional implementations, the protective cover defines an exteriorsurface of a housing of the electronic device that incorporates thedisplay. For increased contrast, a conventional display stack isintentionally designed to be opaque.

An electronic device can also include an optical imaging system, such asa camera or an ambient light sensor. Typically, an optical imagingsystem is positioned below the protective cover, adjacent to, andseparated from, the display stack. As a result, a conventionalelectronic device incorporating both a display stack and an opticalimaging system typically requires a large-area protective cover thatextends beyond a periphery of the display stack in order to reservespace to accommodate the optical imaging system. This conventionalconstruction undesirably increases the apparent size of a bezel regioncircumscribing the display, while also undesirably increasing the sizeand volume of the housing of the electronic device.

SUMMARY

Some embodiments described reference an electronic device including aprotective outer cover. The protective outer cover defines an interfacesurface to receive a touch input from a finger. The device also includesa display positioned below the protective outer cover and an opticalimaging system positioned below the display. The optical imaging systemincludes a light emitting element configured to emit shortwave infraredlight through the display and a photosensitive element opticallyisolated from the light emitting element and configured to receive(through the display) a reflection from the interface surfacecorresponding to a portion of an image of the finger.

Some embodiments described herein reference a method of operating anoptical imaging system positioned below a display of an electronicdevice to capture an image, the method including the operations of:detecting a contact area of a touch input provided to the display by thedisplay; illuminating the contact area with shortwave infrared light bya light emitting element of the optical imaging system; receiving one ormore surface reflections of shortwave infrared light from the contactarea; and assembling an image from the one or more surface reflections.

Some embodiments described herein reference a method of imaging an inputsurface defined by a glass substrate, the method including theoperations of: illuminating the input surface with shortwave infraredlight emitted from one or more light emitting elements; receiving, at anarray of photosensitive elements, one or more surface shortwave infraredlight reflections from the input surface at an array of photosensitiveelements after filtering the one or more surface shortwave infraredlight reflections with a narrow field of view filter; and assembling animage of the input surface based on the received one or more surfaceshortwave infrared light reflections.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to representative embodiments illustrated inthe accompanying figures. It should be understood that the followingdescriptions are not intended to limit this disclosure to one includedembodiment. To the contrary, the disclosure provided herein is intendedto cover alternatives, modifications, and equivalents as may be includedwithin the spirit and scope of the described embodiments, and as definedby the appended claims.

FIG. 1A depicts an electronic device that can incorporate a displaystack suitable for through-display imaging.

FIG. 1B depicts a simplified block diagram of the electronic device ofFIG. 1A.

FIG. 2A depicts an example simplified cross-section of the display stackof FIG. 1A, taken through line A-A, depicting an optical imaging systemoperating outside the shortwave infrared band.

FIG. 2B is a chart depicting cumulative effects of surface andsubsurface reflection(s) received by the optical imaging system of FIG.2A.

FIG. 2C depicts an example simplified cross-section of the display stackof FIG. 1A, taken through line A-A, depicting an optical imaging systemoperating within the shortwave infrared band.

FIG. 2D is a chart depicting cumulative effects of surface andsubsurface reflection(s) received by the optical imaging system of FIG.2C.

FIG. 3A depicts an example simplified cross-section of a display stackincorporating an optical imaging system, operable within the shortwaveinfrared band.

FIG. 3B depicts an example arrangement of pixels of a display stackincorporating an optical imaging system operable within the shortwaveinfrared band.

FIG. 4A depicts an example simplified cross-section of a display stackincorporating an optical imaging system, operable within the shortwaveinfrared band.

FIG. 4B is a detail view of a portion of the optical imaging system ofFIG. 4A.

FIG. 5 is a simplified flow chart depicting example operations of amethod of capturing an image of an object touching a display, such asdescribed herein.

FIG. 6 is a simplified flow chart depicting example operations of amethod of determining an optical property of an object touching adisplay, such as described herein.

The use of the same or similar reference numerals in different figuresindicates similar, related, or identical items.

The use of cross-hatching or shading in the accompanying figures isgenerally provided to clarify the boundaries between adjacent elementsand also to facilitate legibility of the figures. Accordingly, neitherthe presence nor the absence of cross-hatching or shading conveys orindicates any preference or requirement for particular materials,material properties, element proportions, element dimensions,commonalities of similarly illustrated elements, or any othercharacteristic, attribute, or property for any element illustrated inthe accompanying figures.

Similarly, certain accompanying figures include vectors, rays, tracesand/or other visual representations of one or more example paths—whichmay include reflections, refractions, diffractions, and so on, throughone or more mediums—that may be taken by one or more photons originatingfrom one or more light sources shown or, in some cases, omitted from,the accompanying figures. It is understood that these simplified visualrepresentations of light are provided merely to facilitate anunderstanding of the various embodiments described herein and,accordingly, may not necessarily be presented or illustrated to scale orwith angular precision or accuracy, and, as such, are not intended toindicate any preference or requirement for an illustrated embodiment toreceive, emit, reflect, refract, focus, and/or diffract light at anyparticular illustrated angle, orientation, polarization, color, ordirection, to the exclusion of other embodiments described or referencedherein.

Additionally, it should be understood that the proportions anddimensions (either relative or absolute) of the various features andelements (and collections and groupings thereof) and the boundaries,separations, and positional relationships presented therebetween, areprovided in the accompanying figures merely to facilitate anunderstanding of the various embodiments described herein and,accordingly, may not necessarily be presented or illustrated to scale,and are not intended to indicate any preference or requirement for anillustrated embodiment to the exclusion of embodiments described withreference thereto.

DETAILED DESCRIPTION

Embodiments described herein reference an electronic device thatincludes a display and an optical imaging system.

In certain embodiments, the optical imaging system is configured tooperate in at least the shortwave infrared band and is positionedbehind, and/or integrated within, the display of the electronic device.More specifically, the optical imaging system, when in operation, isconfigured to produce a flood illumination of an object or part of anobject in contact with an input surface of the display in the shortwaveinfrared band. In addition, the optical imaging system is configured toreceive and quantify surface and/or subsurface reflections—if any—thatresult from the flood illumination in the shortwave infrared band.

As used herein, the phrase “surface reflection” refers a change inpolarity of at least one direction of propagation of an opticalwavefront (e.g., a ray of light) as a result of interaction with aninterface between two different media having differing refractiveindices. A surface reflection can include both specular reflectioncomponents (e.g., components reflected at the same angle relative to asurface normal to the interface) and diffuse reflection components(e.g., components reflected at a different angle relative to the surfacenormal to the interface).

As used herein, the phrase “subsurface reflection” refers to one or morescattered or refracted components of an optical wavefront (e.g., a rayof light) passing through, or within, a non-transparent or translucentmedium. A subsurface reflection, as described herein, includespredominantly diffuse reflection components.

As a result, when a user of the electronic device touches the inputsurface of the display (for example to interact with content shown onthe display), the optical imaging system can obtain an image and/orotherwise determine one or more properties of that user's finger. Forexample, the optical imaging system can be configured to, withoutlimitation: obtain an image of the user's fingerprint; determine a veinpattern of the user; determine blood oxygenation of the user; determinethe user's pulse; determine whether the user is wearing a glove;determine whether the user's finger is wet or dry; and so on.

The optical imaging system can be any suitable optical imaging system,including both single-element sensors (e.g., photodiodes,phototransistors, photosensitive elements, and so on) and multi-elementsensors (e.g., complementary metal oxide semiconductor arrays,photodiode arrays, and so on).

As noted above, in many embodiments, an optical imaging system, such asdescribed herein, is configured to operate (e.g., to receive and/or emitlight) in at least the shortwave infrared band. As used herein, thephrases “shortwave infrared band” and “shortwave infrared light” andsimilar phrases refer, generally, to the band of infrared lightincluding wavelengths between and including approximately 1,100 nm (1.1μm) to 3,000 nm (3.0 μm).

For example, in some embodiments, an optical imaging system can beconfigured to emit and/or receive light having wavelengths ofapproximately 1450 nm±50 nm. In other embodiments, an optical imagingsystem is configured to emit and/or receive light having wavelengths ofapproximately 1950 nm±50 nm. In still other embodiments, an opticalimaging system is configured to emit and/or receive light havingwavelengths of approximately 1200 nm±50 nm.

For simplicity of description, unless otherwise specified, it may beunderstood that an optical imaging system described herein is configuredto emit and/or receive light having wavelengths of approximately 1450nm±50 nm. It is appreciated, however, that this is merely one exampleand other wavelength bands—or multiple wavelength bands or differentband widths—can be suitable in other implementations of the embodimentsdescribed herein, or equivalents thereof.

As noted above, an optical imaging system can be positioned behind adisplay of an electronic device defining an input surface. In theseexamples, the optical imaging system can be oriented to emit and receivelight at least partially through the display toward and from the inputsurface. For example, in one embodiment, the optical imaging system ispositioned below an organic light emitting diode display. In thisexample, the optical imaging system can emit and receive shortwaveinfrared light through inter-pixel regions of the organic light emittingdiode display.

In another embodiment, a micro light emitting diode display can includean array of pixels defining an active display area below an inputsurface. An array of flood illumination pixels, each configured to emitlight in at least the shortwave infrared band, can be dispersed amongthe pixels defining the active display area. In addition, an array ofphotosensitive elements, each responsive to light in at least theshortwave infrared band, can be dispersed among the pixels defining theactive display area. In these embodiments, the array of floodillumination pixels can be used to illuminate an object in contact withthe input surface and the array of photosensitive elements can be usedto receive reflections from that object that result from the floodillumination.

In yet another embodiment, an organic light emitting diode display caninclude an array of pixels defining an active display area below aninput surface. A backlight layer (which can be back-illuminated orside-illuminated), configured to emit light at least in the shortwaveinfrared band, can be positioned behind the active display area; lightemitted from the backlight layer passes through inter-pixel regions ofthe organic light emitting diode display. In addition, an array ofphotosensitive elements, each responsive to light in at least theshortwave infrared band, can be formed onto the backlight, and separatedfrom the backlight by an opaque masking layer. In these embodiments, thebacklight can be used to illuminate an object in contact with the inputsurface and the array of photosensitive elements can be used to receivereflections from that object that result from the flood illumination.

In some embodiments, an optical imaging system such as described hereincan be used by an electronic device for any suitable imaging, sensing,or data aggregation purpose without contributing to the size of a bezelregion that may surround the display. Example uses include, but are notlimited to: ambient light sensing; proximity sensing; depth sensing;receiving structured light; optical communication; proximity sensing;position-finding; biometric imaging (e.g., fingerprint imaging, irisimaging, facial recognition, vein imaging, and so on); determiningoptical, physical, or biometric properties (e.g., reflection spectrum,absorption spectrum, and so on); and the like.

In some embodiments, multiple discrete optical imaging systems can beassociated with different regions of the same display. For example, afirst optical imaging system can be disposed behind a lower portion of adisplay and a second optical imaging system can be disposed behind anupper portion of the same display. The first and second optical imagingsystems can be configured to receive and/or emit light in the same oroverlapping bands of shortwave infrared or traditionally visible lightor, in other embodiments, in non-overlapping bands of shortwave infraredor traditionally visible light.

More generally, it may be appreciated that different discrete opticalimaging systems associated with the same display can be configured fordifferent purposes or in different ways. Similarly, a single opticalimaging system can be configured to emit and/or receive light inmultiple bands of light, either simultaneously, selectively, or in aparticular sequence or pattern.

As such, for simplicity of description, many embodiments that followreference an example construction in which a single optical imagingsystem is positioned at least partially behind an active display area ofa display of an electronic device. It may be appreciated, however, thatthese embodiments described herein—together with equivalents thereof—maybe altered or adjusted to incorporate discreet optical imaging systemsin a variety of locations relative to a display or non-display surfaceof an electronic device and configured for the same or differentimaging, sensing, or data aggregation purposes. For example, a firstoptical imaging system positioned relative to a first region of anactive display area of a display of an electronic device may beconfigured to illuminate and obtain an image of a fingerprint of a userof that electronic device whereas a second optical imaging systempositioned relative to a second region of the active display area may beconfigured to illuminate and obtain an image of a vein pattern of theuser.

These foregoing and other embodiments are discussed below with referenceto FIGS. 1A-6. However, those skilled in the art will readily appreciatethat the detailed description given herein with respect to these figuresis for explanatory purposes only and should not be construed aslimiting.

FIG. 1A depicts an electronic device 100, including a housing 102 thatencloses a display stack defining a display. The display stack caninclude layers or elements such as, in no particular order: a touchinput layer; a force input layer; an anode layer; a cathode layer; anorganic layer; an encapsulation layer; a reflector layer; a stiffeninglayer; an injection layer; a transport layer; a polarizer layer; ananti-reflective layer; a liquid crystal layer; a backlight layer; one ormore adhesive layers; a compressible layer; an ink layer; a mask layer;and so on.

For simplicity of description, the embodiments that follow reference anorganic light emitting diode display stack including, among otherlayers: a reflective backing layer; a thin-film transistor layer; anencapsulation layer; and an emitting layer. It is appreciated, however,that this is merely one illustrative example implementation and thatother displays and display stacks can be implemented with other displaytechnologies, or combinations thereof.

The display stack also typically includes an input sensor (such as aforce input sensor and/or a touch input sensor) to detect one or morecharacteristics of a user's physical interaction with an active displayarea 104 of the display of the electronic device 100. The active displayarea 104 is typically characterized by an arrangement ofindividually-controllable, physically-separated, and addressable pixelsor subpixels distributed at one or more pixel densities and in one ormore pixel or subpixel distribution patterns.

Example input characteristics that can be detected by an input sensor ofthe electronic device 100 include, but are not limited to: touchlocation; force input location; touch gesture path, length, duration,and/or shape; force gesture path, length, duration, and/or shape;magnitude of force input; number of simultaneous force inputs; number ofsimultaneous touch inputs; and so on.

As a result of these constructions, a user 106 of the electronic device100 may be encouraged to interact with content shown in the activedisplay area 104 of the display by physically touching and/or applying aforce with the user's finger to the input surface above an arbitrary orspecific region of the active display area 104.

In these embodiments, as with other embodiments described herein, thedisplay stack is additionally configured to facilitate through-displayimaging of the user's fingerprint when the user 106 touches the displayto interact with content shown in the active display area 104.

More specifically, in one example, the display stack defines an imagingaperture (not shown) through a backing layer of the display stack,thereby permitting light to travel through the display stack between twoor more organic light emitting diode subpixels or pixels (herein,“inter-pixel” regions). In some cases, the imaging aperture takes arectangular shape and is disposed on a lower region of the activedisplay area 104, but this may not be required. In other cases, theimaging aperture takes a circular or oval shape and is disposed in acentral region of the active display area 104. Typically, the imagingaperture is larger than the fingerprint of the user 106, but this maynot be required and smaller apertures may be suitable. For example, insome embodiments, the backing layer may be omitted entirely; the imagingaperture may take the same size and shape as the active display area104.

As noted with respect to other embodiments described herein, theelectronic device 100 also includes an optical imaging system (notshown). The optical imaging system is positioned at least partiallybelow the imaging aperture in order to collect and quantify lightdirected through the inter-pixel regions of the display stack. As aresult of this construction, the electronic device 100 can obtain animage of the fingerprint of the user 106; this operation is referred toherein as a “fingerprint imaging operation.”

In some embodiments, the optical imaging system of the electronic device100 illuminates the finger of the user 106 during a fingerprint imagingoperation with light in the shortwave infrared band at approximately1450 nm±50 nm. Light in the shortwave infrared band may be selected tomaximize absorption of light within the finger of the user 106, therebyminimizing or eliminating remittance reflections (e.g., light at leastpartially reflected and diffused by the subsurface layers of the user'sskin) that may otherwise be received by the optical imaging system asnoise. For example, it may be appreciated that water content in the skinof the user 106 may absorb a greater quantity of light at wavelengthsapproximately equal to 1200 nm, 1450 nm, and 1950 nm than othertraditionally visible or traditionally non-visible frequencies.Accordingly, in many embodiments, while performing a fingerprint imagingoperation, the optical imaging system of the electronic device 100 maybe configured to operate at 1200 nm, 1450 nm, and/or 1950 nm.

In some embodiments, the optical imaging system of the electronic device100 illuminates a region of the display below the finger of the user106, as detected by the input sensor of the electronic device 100, withshortwave infrared light. In other examples, the optical imaging systemilluminates a perimeter of the user's finger with shortwave infraredlight. In some examples, the optical imaging system of the electronicdevice 100 illuminates discrete portions of the finger of the user 106in sequence or in a particular pattern with shortwave infrared light atone or multiple frequencies or discrete bands.

In view of the preceding examples, it may be appreciated thatillumination of the finger of the user 106 with shortwave infrared lightduring a fingerprint imaging operation can occur in a number of suitableways. For example, in some cases, the optical imaging system of theelectronic device 100 illuminates the user's finger with pulsed(continuous or discrete) or steady light in the shortwave infrared band.In other examples, the optical imaging system of the electronic device100 illuminates the finger of the user 106 with shortwave infrared lightemitted with a particular modulation pattern or frequency.

In further examples, the optical imaging system of the electronic device100 illuminates the finger of the user 106 by alternating betweenfrequencies or bands of light within the shortwave infrared band at aparticular frequency, modulation, pulse pattern, waveform and so on.

In still other examples, the optical imaging system of the electronicdevice 100 illuminates the finger of the user 106 while the activedisplay area 104 of the display of the electronic device 100 alsorenders a visible-light image. In other words, from the perspective ofthe user 106, the portion(s) of the display below the fingerprint maynot be specially or differently illuminated from other portions of thedisplay; the display can continue to render whichever static or animatedimage or series of images appeared on the display prior to the usertouching the display. In still further examples, while the opticalimaging system is performing a fingerprint imaging operation, thedisplay of the electronic device 100 can locally increase or decreasebrightness below the user's finger, can locally increase or decreasecontrast below the user's finger, can locally increase or decreasesaturation below the user's finger, and so on.

In other examples, the optical imaging system of the electronic device100 need not illuminate the finger of the user 106 with only shortwaveinfrared light. For example, the optical imaging system may also beconfigured to illuminate the finger of the user 106 with green and/orblue visible light in order to detect or otherwise determine the user'spulse or blood oxygen content. In some cases, the optical imaging systemis configured to perform a fingerprint imaging operation substantiallysimultaneously with an operation to detect the pulse of the user 106 toincrease confidence that the fingerprint image obtained by thefingerprint imaging operation corresponds to a biological fingerprint.

It may be appreciated that the foregoing description of FIG. 1A, and thevarious alternatives thereof and variations thereto, are presented,generally, for purposes of explanation, and to facilitate a thoroughunderstanding of various possible configurations of an electronic deviceincorporating a display stack suitable for through-display imaging, suchas described herein. However, it will be apparent to one skilled in theart that some of the specific details presented herein may not berequired in order to practice a particular described embodiment, or anequivalent thereof. For simplicity of description and illustration, FIG.1B is provided. This figure depicts a simplified block diagram of theelectronic device of FIG. 1A showing various operational and structuralcomponents that can be included in an electronic device configured tothrough-display imaging such as described herein.

In particular, the electronic device 100 includes a protective outercover 108. The protective outer cover 108 defines an input surface forthe user 106 and, additionally, protects and encloses various componentsof the electronic device 100, including the optical imaging system,introduced and described in greater detail below. The protective outercover 108 can be a single or multi-layer substrate made from any numberof suitable materials, whether transparent, translucent, or opaque,including, but not limited to, glass, plastic, acrylic, polymermaterials, organic materials, and so on. In many embodiments, theprotective outer cover 108 is formed from a material transparent toshortwave infrared light, such as glass.

The electronic device 100 also includes an input sensor 110 disposed atleast partially below the protective outer cover 108. The input sensor110 can be any suitable input sensor including, but not limited to: acapacitive input sensor; a resistive input sensor; an inductive inputsensor; an optical input sensor; and so on. The input sensor 110 can beconfigured to detect any suitable user input or combination of userinputs including, but not limited to: touch gestures; touch inputs;multi-touch inputs; force inputs; force gestures; multi-force inputs;pressure inputs; thermal inputs; acoustic inputs; and so on. In typicalembodiments, the input sensor 110 is substantially transparent (e.g.,exhibiting a transmittance of light greater than 80%), but this may notbe required of all embodiments.

The electronic device 100 also includes a display stack 112 which can bedisposed below the input sensor 110. The display stack 112 can be formedfrom a number of independent layers of material or materials thatcooperate to define the display and the active display area 104 (see,e.g., FIG. 1A). In many examples, the display stack 112 defines anorganic light emitting diode display, but this may not be required. Forexample, in other cases, the display stack 112 can define, withoutlimitation: a micro light emitting diode display; a liquid crystaldisplay; an electronic ink display; a quantum dot display; and so on.

As noted with respect to other embodiments described herein, the displaystack 112 can define an array of discrete pixels that are independentlyaddressable and controllable. The pixels of the display stack 112 can bedisposed at a constant pitch or a variable pitch to define a singlepixel density or one or more pixel densities.

As noted with respect to other embodiments described herein, the activedisplay area 104 of the display stack 112 is positioned at leastpartially above the optical imaging system, identified in the figure asthe optical imaging system 114. As a result of this construction, theoptical imaging system 114 can receive light transmitted through theinter-pixel regions of the active display area 104 of the display stack112.

The optical imaging system 114 can include a number of light emittingand light detecting elements including one or more photosensitiveelements arranged in any suitable pattern. In many examples, the opticalimaging system 114 is a low fill-factor array of phototransistor orphotodiode elements, disposed above or below or coplanar with the activedisplay area 104 of the display, but this may not be required of allembodiments.

The optical imaging system 114, the display stack 112, and the inputsensor 110—among other elements, modules, or components of theelectronic device 100—are communicably coupled to a processor 116. Theprocessor 116 can be any suitable processor or circuitry capable ofperforming, monitoring, or coordinating one or more processes oroperations of the electronic device 100. The processor 116 can be anysuitable single-core or multi-core processor capable to executeinstructions stored in a memory (not shown) to instantiate one or moreclasses or objects configured to interface with an input or output ofone or more of the optical imaging system 114, the display stack 112,and/or the input sensor 110. In some examples, the processor 116 may bea dedicated processor associated with one or more of the optical imagingsystem 114, the display stack 112, and/or the input sensor 110. In othercases, the processor 116 may be a general purpose processor.

In still other embodiments, the electronic device 100 can include one ormore optional optical components 118. The optional optical components118 are typically positioned between the optical imaging system 114 andthe display stack 112 and can include, but may not be limited to: one ormore lenses, filters, mirrors, actuators, apertures, irises, flashelements, narrow field of view filters, collimators, flood illuminators,or other accessory optical elements, or combinations thereof.

As noted above, the electronic device 100 can also include an imagingaperture 120 defined into or through one or more opaque or substantiallyopaque layers of the display stack 112. The imaging aperture 120 istypically aligned with the optical imaging system 114. As noted withrespect to other embodiments described herein, the imaging aperture 120can take any suitable size or shape.

Accordingly, generally and broadly in view of FIGS. 1A-1B, it isunderstood that an electronic device including a display suitable forthrough-display imaging can be configured in a number of ways. Forexample, although the electronic device 100 is depicted as a cellularphone, it may be appreciated that other electronic devices canincorporate a display stack such as described herein including, but notlimited to: tablet devices; laptop devices; desktop computers; computingaccessories; peripheral input devices; vehicle control devices; mobileentertainment devices; augmented reality devices; virtual realitydevices; industrial control devices; digital wallet devices; homesecurity devices; business security devices; wearable devices; healthdevices; implantable devices; clothing devices; fashion accessorydevices; and so on.

Further it is appreciated that beyond the components depicted in FIGS.1A-1B, the electronic device can also include one or more processors,memory, power supplies and/or batteries, network connections, sensors,input/output ports, acoustic elements, haptic elements, digital and/oranalog circuits for performing, supervising, and/or coordinating one ormore tasks of the electronic device 100, and so on. For simplicity ofillustration, the electronic device 100 is depicted in FIGS. 1A-1Bwithout many of these elements, each of which may be included, partiallyand/or entirely, within the housing 102 and may be operationally orfunctionally associated with, or coupled to, the display of theelectronic device 100.

Further, although the electronic device 100 includes only a singlerectangular display, it may be appreciated that this example is notexhaustive. In other embodiments, an electronic device can include, ormay be communicably coupled to, multiple displays, one or more of whichmay be suitable for through-display imaging. Such accessory/auxiliarydisplays can include, but may not be limited to: secondary monitors;function row or keyboard key displays; wearable electronic devicedisplays; peripheral input devices (e.g., trackpads, mice, keyboards,and so on) incorporating displays; digital wallet screens; and so on.Similarly, a rectangular display may not be required; other embodimentsare implemented with displays taking other shapes, includingthree-dimensional shapes (e.g., curved displays).

Similarly, although the display described in reference to the electronicdevice 100 is a primary display of an electronic device, it isappreciated that this example is not exhaustive. In some embodiments, adisplay stack can define a low-resolution auxiliary display, such as amonochromatic display or a greyscale display. In other cases, a displaystack can define a single-image display, such as a glyph or icon. In onespecific example, a power button for an electronic device can include abutton cap incorporating a display such as described herein. The displaycan be configured to selectively display a power icon and/or a limitedset of icons or glyphs associated with one or more functions the buttonmay be configured to perform, or one or more configurable options thebutton is associated with (e.g., power options, standby options, volumeoptions, authentication options, digital purchase options, userauthentication options, and so on). In these examples, alimited-purpose, auxiliary, or secondary display can be configured tohave partial transparency or translucency, such as described herein, tofacilitate through-display imaging.

Thus, it is understood that the foregoing descriptions of specificembodiments are presented for the purposes of illustration anddescription. These descriptions are not exhaustive nor intended to limitthe disclosure to the precise forms recited herein. To the contrary, itwill be apparent to one of ordinary skill in the art that manymodifications and variations are possible in view of the aboveteachings. Particularly, it is understood that a display stack suitablefor through-display imaging can be constructed and/or assembled in manysuitable ways. For example, many embodiments described herein referencemethods, constructions, and architectures that promote increased opticaltransmissivity through the display stack above an imaging aperture.

Certain example implementations of an optical imaging system positionedbelow an input surface of a display stack of an electronic device aredepicted in FIGS. 2A-2D. In particular, FIG. 2A depicts a simplifiedexample cross-section of the display stack of FIG. 1A, touched by auser, taken through line A-A, depicting an optical imaging systempositioned below the display stack.

More specifically, FIG. 2A depicts an optical imaging system 200disposed at least partially behind a display stack 202 that defines adisplay (e.g., an organic light emitting diode display, a micro lightemitting diode display, a liquid crystal display, and so on) tofacilitate imaging of a fingerprint of a user 204 through the displaystack 202.

For simplicity of illustration and description, the display stack 202 inthe illustrated embodiment is simplified to a single layer, but it maybe appreciated that the display stack 202 can include multiple discretesingle or multi-function layers that can include, without limitation orspecific requirement: a protective outer cover; an emitting layer (alsoreferred to as a pixel layer); an opaque or reflective backing layer; athin-film transistor layer; a capacitive touch sensing layer; a forcesensing layer; a backlight layer; a polarizer layer; and so on.

A protective outer cover that may be included in the display stack 202is typically formed from an optically transparent substrate materialsuch as glass, acrylic, plastic, or the like. In many examples, aprotective outer cover defines an input surface that can be touched bythe user 204. In many examples, the protective outer cover defines atleast a portion of an exterior surface of a housing of an electronicdevice, such as the housing 102 of the electronic device 100 depicted inFIG. 1A. In other words, for embodiments in which the display stack 202is coupled to or otherwise includes a protective outer cover, theprotective outer cover may at least partially enclose and/or seal one ormore other layers of the display stack 202, such as an emitting layer oran opaque or reflective backing layer.

The optical imaging system 200 also includes one or more opticaltransducer modules, typically positioned at least partially below thedisplay stack 202. The optical transducer modules may be configured to(1) emit light and (2) to receive light and can include one or morecomponents such as, but not limited to: photodiodes; laser diodes; lightemitting diodes; phototransistors; and so on. In the illustratedexample, two optical transducer modules are shown and identified as theoptical transducer module 206 and the optical transducer module 208.

The optical transducer modules 206, 208 of the optical imaging system200 can be communicably coupled to a processor or a processing circuitry(not shown) via a circuit board. The circuit board can be formed from arigid or flexible substrate. The processor or processing circuitry canbe a general purpose processor or circuitry or an application-specificprocessor or circuitry configured for, in many examples, encrypted orotherwise secure data processing and/or storage.

As a result of the depicted construction, an image of the fingerprint ofthe user 204—and in particular, an image that distinguishes betweenridge and valley features of the fingerprint—can be obtained by theoptical imaging system 200 through the display stack 202. In theillustrated embodiment, a valley feature of the fingerprint of the user204 is shown and identified as the valley feature 204 a. Similarly, aridge feature of the fingerprint of the user 204 is shown and identifiedas the ridge feature 204 b. An air gap 204 c separates the valleyfeature 204 a from the display stack 202. It may be appreciated that theair gap 204 c can also be occupied, in part or entirely by, withoutlimitation, detritus, oils, gasses, liquids, and so on. For simplicityof illustration and description, the air gap 204 c is depicted withoutsuch elements.

During a fingerprint imaging operation, the optical transducer modules206, 208 can be separately, sequentially, or simultaneously illuminated(e.g., in response to a signal sent by a processor or processingcircuitry) in a band outside the shortwave infrared wavelength band(with any suitable modulation, amplitude, color or spectrum, and so on)when the user 204 touches the protective outer cover.

Light emitted from the optical transducer modules 206, 208 is directedtoward the fingerprint of the user 204 and, in turn, is reflected backinto the display stack 202 by the various features of the user'sfingerprint in contact with the outer layer (e.g., the input surface) ofthe display stack 202.

More particularly, in the illustrated example, light is emitted from theoptical transducer module 208 into the display stack 202, at a selectedfrequency (more generally, in a narrow band of frequencies, representedin the figure with a normal distribution), and generally directed towardthe valley feature 204 a of the fingerprint of the user 204. The path ofthe light emitted from the optical transducer module 208 as it passesthrough the display stack 202 is represented by the ray u₁.

After passing through the display stack 202, the ray u₁ reaches anoptical interface defined between the outer layer of the display stack202 and the air gap 204 c. As may be appreciated, the refractive indicesof the display stack 202 (identified in FIG. 2A as n₁) and the air gap204 c (identified in FIG. 2A as n₃) may be mismatched and, as such, theray u₁ may partially reflect from the interface and may partiallytraverse the interface. Reflection(s) from the interface defined betweenthe outer layer of the display stack 202 and the air gap 204 c arecollectively represented in the figure by the ray u_(1′). In addition,portions of the ray u₁ that traverse the interface are collectivelyrepresented in the figure by the ray u₂. In typical configurations andimplementations, it may be appreciated that the ray u_(1′) is primarilya surface reflection.

After passing through the air gap 204 c, the ray u₂ reaches an opticalinterface defined between a portion of an outer layer of the valleyfeature 204 a of the fingerprint of the user 204 and the air gap 204 c.As may be appreciated, the refractive indices of the outer layer of thevalley feature 204 a (identified in FIG. 2A as n₂) and the air gap 204 c(identified in FIG. 2A as n₃) may be mismatched and, as such, the ray u₂may partially reflect from the interface and may partially traverse theinterface. Reflection(s) from the interface defined between the outerlayer of the valley feature 204 a and the air gap 204 c are collectivelyrepresented in the figure by the ray u_(2′). In addition, portions ofthe ray u₂ that traverse the interface are collectively represented inthe figure by the ray u₃. In typical configurations and implementations,it may be appreciated that the ray u_(2′) can include both surfacereflection components and subsurface reflection components.

After passing into the valley feature 204 a of the fingerprint of theuser 204, the ray u₂ may be diffused throughout the various layers ofthe skin of the user 204. This light is represented in the figure by theray u_(3′). In typical configurations and implementations, it may beappreciated that the ray u_(3′) is primarily a subsurface reflection.

After diffusing and reflecting through various features within thevalley feature 204 a of the fingerprint of the user 204, a portion ofthe ray u_(3′) can return to the optical interface defined between theouter layer of the valley feature 204 a of the fingerprint of the user204 and the air gap 204 c. As noted above, because the refractiveindices of the outer layer of the valley feature 204 a (identified inFIG. 2A as n₂) and the air gap 204 c (identified in FIG. 2A as n₃) maybe mismatched, the ray u_(3′) may partially reflect from the interface(returning into the valley feature 204 a of the fingerprint of the user204) and may partially traverse the interface into the air gap 204 c.The portions of the ray u_(3′) that traverse the interface into the airgap 204 c are collectively represented in the figure by the ray u₄. Intypical configurations and implementations, it may be appreciated thatthe ray u₄, like the ray u_(3′), includes primarily subsurfacereflection components.

After passing through the air gap 204 c, the ray u₄ returns to theoptical interface defined between the outer layer of the display stack202 and the air gap 204 c. Once again, as noted above, because therefractive indices of the display stack 202 (identified in FIG. 2A asn₁) and the air gap 204 c (identified in FIG. 2A as n₃) may bemismatched, the ray u₄ may partially reflect from the interface,returning toward the valley feature 204 a of the fingerprint of the user204, and may partially traverse the interface into the display stack202. Portions of the ray u₄ that traverse the interface and return tothe display stack 202 are collectively represented in the figure by theray u₅. As with the ray u₄, in typical configurations andimplementations, it may be appreciated that the ray u₅ includesprimarily subsurface reflection components.

In addition, in the illustrated embodiment, light is emitted from theoptical transducer module 206 into the display stack 202, at a selectedfrequency, and generally directed toward the ridge feature 204 b of thefingerprint of the user 204. In this example, the path of the lightemitted from the optical transducer module 206 as it passes through thedisplay stack 202 is represented by the ray v₁.

After passing through the display stack 202, the ray v₁ reaches anoptical interface defined between the outer layer of the display stack202 and the ridge feature 204 b of the fingerprint of the user 204. Asmay be appreciated, the refractive indices of the display stack 202(identified in FIG. 2A as n₁) and the ridge feature 204 b (identified inFIG. 2A as n₂) may be mismatched and, as such, the ray v₁ may partiallyreflect from the interface and may partially traverse the interface.Reflection(s) from the interface defined between the outer layer of thedisplay stack 202 and the ridge feature 204 b are collectivelyrepresented in the figure by the ray v_(1′). In addition, portions ofthe ray v₁ that traverse the interface are collectively represented inthe figure by the ray v₂. In typical configurations and implementations,it may be appreciated that the ray v_(1′) is primarily a surfacereflection.

After passing into the ridge feature 204 b of the fingerprint of theuser 204, the ray v₂ may be diffused throughout the various layers ofthe skin of the user 204. This light is represented in the figure as theray v_(2′). As may be appreciated, some of the light corresponding toray v_(2′) may exit the ridge feature 204 b of the fingerprint of theuser 204 and return to the display stack 202. This light is representedin the figure by the ray v₃. As with the ray u₅, in typicalconfigurations and implementations, it may be appreciated that the rayv₃ includes primarily subsurface reflection components.

In this manner, when the optical transducer modules 206, 208 emit lighttoward the fingerprint of the user 204, both surface and subsurfacereflections are reflected back which reduces the detectable contrastbetween the ridge and valley features of the fingerprint of the user204. In particular, it may be appreciated that contrast is reduced inpart because subsurface reflections and surface reflections oftenexhibit opposite polarity.

More specifically, as shown in FIG. 2A, subsurface reflections may begreater in magnitude for ridge regions of a fingerprint than for valleyregions of the same fingerprint (see, e.g., the subsurface reflectionsrepresented by the rays v₃ and u₅). In other words, for subsurfacereflections, ridges appear “brighter” than valley regions of afingerprint. Oppositely, surface reflections may be greater in magnitudefor valley regions of a fingerprint than for ridge regions of the samefingerprint (see, e.g., the surface reflections represented by the raysu_(1′) and v_(1′)). In other words, for surface reflections, valleysappear “brighter” than ridges regions of a fingerprint. These oppositeeffects can result in substantially reduced contrast. For example, asshown in the chart depicted in FIG. 2B, both the valley feature 204 aand the ridge feature 204 b of the fingerprint of the user 204 areassociated with a magnitude of reflected light that results from acombination of surface reflections and subsurface reflections. Thesecombined reflections can undesirably reduce the performance (e.g., thedetectable contrast between valleys and ridges) of the optical imagingsystem 200.

Accordingly, many embodiments described herein operate an opticalimaging system in the shortwave infrared band which, as noted above,includes wavelengths absorbed to a high degree by the water present in auser's finger. For example, FIG. 2C depicts an optical imaging system200 disposed at least partially behind a display stack 202 that definesa display to facilitate imaging of a fingerprint of a user 204 throughthe display stack 202. The optical imaging system 200 can be configuredin the same manner as described in reference to FIG. 2A; thisdescription is not repeated.

In contrast to the embodiment depicted in FIG. 2A, during a fingerprintimaging operation, the optical transducer modules 206, 208 can beseparately, sequentially, or simultaneously illuminated (e.g., inresponse to a signal sent by a processor or processing circuitry) in ashortwave infrared wavelength band that is absorbed to a high degree bywater (e.g., 1450 nm±50 nm), when the user 204 touches the display stack202.

In this example, light emitted from the optical transducer modules isdirected toward the fingerprint of the user 204 which, in turn, isreflected back into the display stack 202 by the various features of theuser's fingerprint in contact with the outer layer (e.g., the inputsurface) of the display stack 202. However, because of the selectedwavelength of light, any light that traverses an optical interfaceboundary will be absorbed by the water in the finger of the user 204,effectively reducing and/or eliminating subsurface reflections.

More particularly, in the illustrated example, light is emitted from theoptical transducer module 208 into the display stack 202, at a selectedfrequency, and generally directed toward the valley feature 204 a of thefingerprint of the user 204. As with the embodiment depicted in FIG. 2A,the path of the light emitted from the optical transducer module 208 asit passes through the display stack 202 is represented by the ray u₁.

After passing through the display stack 202, the ray u₁ reaches anoptical interface defined between the outer layer of the display stack202 and the air gap 204 c. As the refractive indices of the displaystack 202 (n₁) and the air gap 204 c (n₃) may be mismatched, the ray u₁may partially reflect from the interface and may partially traverse theinterface. As with the embodiment depicted in FIG. 2A, reflection(s)from this interface are collectively represented in the figure by theray u_(1′). In addition, portions of the ray u₁ that traverse theinterface are collectively represented in the figure by the ray u₂. Intypical configurations, as noted above, the ray u_(1′) is primarily asurface reflection.

After passing through the air gap 204 c, the ray u₂ reaches the opticalinterface defined between the outer layer of the valley feature 204 a ofthe fingerprint of the user 204 and the air gap 204 c. Because therefractive indices of the outer layer of the valley feature 204 a (n₂)and the air gap 204 c (n₃) can be mismatched, the ray u₂ may partiallyreflect from the interface and may partially traverse the interface. Aswith the embodiment depicted in FIG. 2A, reflection(s) from thisinterface are collectively represented in the figure by the ray u_(2′)and portions of the ray u₂ that traverse the interface are collectivelyrepresented in the figure by the ray u₃. In typical configurations andimplementations, it may be appreciated that the ray u_(2′) can includeboth surface reflection components and subsurface reflection components.

In contrast to the embodiment described in reference to FIG. 2A, afterpassing into the valley feature 204 a of the fingerprint of the user204, the ray u₂ may be substantially absorbed by water in the variouslayers of the skin of the user 204.

As with the embodiment described in reference to FIG. 2A, light can alsobe emitted from the optical transducer module 206 into the display stack202, at a selected frequency, and generally directed toward the ridgefeature 204 b of the fingerprint of the user 204. As with the embodimentdescribed in reference to FIG. 2A, the path of the light emitted fromthe optical transducer module 206 as it passes through the display stack202 is represented by the ray v₁.

As with previously described embodiments, after passing through thedisplay stack 202, the ray v₁ reaches the optical interface definedbetween the outer layer of the display stack 202 and the ridge feature204 b of the fingerprint of the user 204. As noted above, the refractiveindices of the display stack 202 (n₁) and the ridge feature 204 b (n₂)may be mismatched and, as such, the ray v₁ may partially reflect fromthe interface and may partially traverse the interface. As with otherembodiments described herein, reflection(s) from this interface arecollectively represented in the figure by the ray v_(1′) whereasportions of the ray v₁ that traverse the interface are collectivelyrepresented in the figure by the ray v₂. As noted above, the ray v_(1′)is primarily a surface reflection.

After passing into the ridge feature 204 b of the fingerprint of theuser 204, the ray v₂ may be absorbed by the water within the variouslayers of the skin of the user 204.

In this manner, when the optical transducer modules 206, 208 emitshortwave infrared light toward the fingerprint of the user 204,substantially only surface reflections are reflected back whichsubstantially increases the detectable contrast between the ridge andvalley features of the fingerprint of the user 204. For example, asshown in the chart depicted in FIG. 2D, only the valley feature 204 a ofthe fingerprint of the user 204 is associated with a certain magnitudeof reflected light.

It may be appreciated that the foregoing description of FIGS. 2A-2D, andvarious alternatives thereof and variations thereto are presented,generally, for purposes of explanation, and to facilitate anunderstanding of various possible operational frequencies of opticalimaging systems, such as described herein. However, it will be apparentto one skilled in the art that some of the specific details presentedherein may not be required in order to practice a particular describedembodiment, or an equivalent thereof.

Thus, it is understood that the foregoing descriptions of specificembodiments are presented for the purposes of illustration anddescription. These descriptions are not exhaustive nor intended to limitthe disclosure to the precise forms recited herein. To the contrary, itwill be apparent to one of ordinary skill in the art that manymodifications and variations are possible in view of the aboveteachings. Particularly, it is understood that an optical imaging systemcan be formed in a display stack in a number of suitable ways.

For example, FIG. 3A depicts an example simplified cross-section of adisplay stack incorporating at least a portion of an optical imagingsystem, operable within the shortwave infrared band, such as describedherein. In this example, a display stack 300 includes an outerprotective layer 302 that is positioned above a pixel layer 304. Theouter protective layer 302 can be formed from any number of suitabletransparent materials such as, but not limited to: glass, plastic,acrylic, sapphire, and so on.

It may be appreciated that the display stack 300 is presented in FIG. 3Ain a simplified manner; as with the embodiments depicted in FIGS. 2A and2C, it is appreciated that, for simplicity of illustration, variouslayers of the display stack 300 are omitted from the figure including,but not limited to: thin-film transistor layers; backlight layers;encapsulation layers; cathode layers; anode layers; color mask layers;polarizer layers; and so on.

The pixel layer 304 can be any suitable pixel layer including, but notlimited to: an organic light emitting diode emitter layer; a micro lightemitting diode layer; and so on. As with other embodiments describedherein, the outer protective layer 302 not only protects the pixel layer304 (and/or other layers within and/or required by a display stack) butthe outer protective layer 302 may also define an input surface that maybe touched by a user, such as the user 306.

In this embodiment, an optical imaging system can be partiallyintegrated into the pixel layer 304 of the display stack 300. Moreparticularly, an array of flood illumination pixels—one of which isidentified as the flood illumination pixel 308—can be dispersed amongthe pixels of the pixel layer 304. Each flood illumination pixel 308 ofthe array of flood illumination pixels can be configured to emit lightin one or more bands of light within the shortwave infrared band. Forexample, in one embodiment, a first subset of the array of floodillumination pixels may be configured to emit light at 1450 nm whereas asecond subset of the array of flood illumination pixels may beconfigured to emit light at 1950 nm. In other cases, some of the floodillumination pixels of the array of flood illumination pixels can beconfigured to emit light in the near-infrared band or the visible bandof light, but this may not be required of all embodiments.

In typical examples, the flood illumination pixels of the array of floodillumination pixels are simultaneously illuminated during a fingerprintimaging operation, but this may not be required. For example, in somecases, each flood illumination pixel may be individually addressableand/or controllable. In these and related examples, the array of floodillumination pixels can be coupled to a display controller (not shown)that is also configured to drive the various pixels of the pixel layer304. In other cases, the array of flood illumination pixels can becoupled to a dedicated controller, separate from the display controller.

The array of flood illumination pixels can be dispersed in any suitablepattern or configuration among the pixels of the pixel layer 304. Forexample, FIG. 3B depicts an example arrangement of pixels of the displaystack 300. In this example, the flood illumination pixel 308 can bepositioned adjacent to, and coplanar with, a red subpixel 310, a bluesubpixel 312, and a green subpixel 314.

Although the array of flood illumination pixels, including the floodillumination pixel 308, generally take the shape of a square in theillustrated embodiment, it may be appreciated that this is merely oneexample embodiment. Other shapes, layouts, and configurations arepossible.

FIG. 4A depicts an example simplified cross-section of another opticalimaging system, operable within the shortwave infrared band, that can beincorporated into and/or positioned behind a display stack. FIG. 4Bdepicts a detail view of a portion of the optical imaging system of FIG.4A. In this example, a display stack 400 includes a protective outercover 402 positioned above a pixel layer 404 (that selectively orentirely omits any opaque backing layer or reflective backing layer).The protective outer cover 402 defines an input surface that can betouched by a user 406. The display stack 400, the protective outer cover402, and the pixel layer 404 can, in many cases, be configured in asimilar manner to the embodiments described above in reference to FIGS.2A, 2C, and FIG. 3A; this description is not repeated.

In this example embodiment, the optical imaging system can be positionedbehind the pixel layer 404 of the display stack 400. As illustrated, theoptical imaging system includes a narrow field of view filter 408, aphotodetector stack 410, a thin-film transistor layer 412, a floodlightwaveguide 414, a light emitting element 416, and a floodlight aperture418.

As with other embodiments described herein, the optical imaging systemdepicted in FIGS. 4A-4B is configured to both emit light and to detectlight, specifically in the shortwave infrared band. In the illustratedembodiment, the optical imaging system is positioned behind the pixellayer 404 and, due at least in part to the fact that the pixel layer 404omits an opaque backing, can both receive and transmit light through theinter-pixel regions of the pixel layer 404.

More specifically, in order to emit light, the optical imaging system ofthis embodiment includes a floodlight waveguide 414 positioned behind afloodlight aperture 418 that, in turn, is generally vertically alignedwith at least one inter-pixel region of the pixel layer 404 of thedisplay stack 400. A light emitting element 416 is optically coupled tothe floodlight waveguide 414, and may be physically positioned along aperiphery of the floodlight waveguide 414 (e.g., a side-firingconfiguration). As a result of this construction, light emitted from thelight emitting element 416 can be guided toward, and emitted from, thefloodlight aperture 418 by the floodlight waveguide 414. Further, due tothe relative positioning of the floodlight aperture 418 and the at leastone inter-pixel region of the pixel layer 404 of the display stack 400,light emitted through the floodlight aperture 418 can be transmittedthrough the pixel layer 404, and, thereafter, through the protectiveouter cover 402. In this manner, the optical imaging system isconfigured to emit light toward the user 406 to illuminate thefingerprint of the user 406.

In addition, in order to detect light, the optical imaging systemincludes a photodetector stack 410 positioned below the narrow field ofview filter 408 and disposed on a thin-film transistor layer 412 thatis, in turn, coupled to and positioned above the floodlight waveguide414. As used herein, the phrase “narrow field of view” refers to anoptical filter or element configured to transmit light directed on apath substantially normal to (e.g., within 20-30 degrees, in someexamples, of normal) the optical filter and configured to reject light(e.g., block light) directed on other paths.

The photodetector stack 410 includes a photosensitive element 410 a andan opaque mask layer 410 b. The opaque mask layer 410 b is formed froman optically opaque material so as to optically isolate thephotosensitive element 410 a from the floodlight waveguide 414. In manycases, the opaque mask layer 410 b is formed or otherwise disposed ontothe thin-film transistor layer 412 and/or the floodlight waveguide 414.

As a result of this construction, in order to perform a fingerprintimaging operation, the optical imaging system drives the light emittingelement 416 in order to generate a flood illumination, through the pixellayer 404 and the protective outer cover 402, of the fingerprint of theuser 406 with shortwave infrared light. As described above in referenceto FIGS. 2B-2C, one or more surface reflections, corresponding to valleyfeatures of the fingerprint of the user 406 are thereafter reflecteddownwardly through the protective outer cover 402. A percentage of thereflected rays may traverse the pixel layer 404 through one or moreinter-pixel regions. Thereafter, surface reflections of the fingerprintof the user 406 that are directed substantially normal to the narrowfield of view filter 408 pass through the filter and illuminate thephotosensitive element 410 a that, in response, can generate orotherwise cause a change in an electrical signal. Thereafter, thethin-film transistor layer 412 can convey one or more electrical signalsobtained from the photosensitive elements of the optical imaging systemto a processor or circuit for processing.

It may be appreciated that the foregoing description of FIGS. 3A-4B, andvarious alternatives thereof and variations thereto, are presented,generally, for purposes of explanation, and to facilitate anunderstanding of various possible configurations and constructions of anoptical imaging system, such as described herein. However, it will beapparent to one skilled in the art that some of the specific detailspresented herein may not be required in order to practice a particulardescribed embodiment, or an equivalent thereof.

Thus, it is understood that the foregoing descriptions of specificembodiments are presented for the purposes of illustration anddescription. These descriptions are not exhaustive nor intended to limitthe disclosure to the precise forms recited herein. To the contrary, itwill be apparent to one of ordinary skill in the art that manymodifications and variations are possible in view of the aboveteachings. Particularly, it is understood that an optical imaging systemcan be formed in a display stack in a number of suitable ways.

For example, it may be appreciated that the examples shown in FIGS.3A-4B are not exhaustive. In other cases, an optical imaging system canbe constructed in a different manner. For example, in some embodiments,a floodlight waveguide may not be required; an optical imaging sensorcan be illuminated with backside illumination. In other cases, acombination of backside and side-firing illumination may be implemented.In still further embodiments, as noted above, more than one lightemitting element—each configured to emit light at a differentfrequency—can be optically coupled to a floodlight waveguide, such asdescribed herein. In these embodiments, each light emitting element canbe associated with a particular spectrum or bandwidth suitable for aparticular type or technique of optical imaging. For example, it may beappreciated that vein imaging may be efficiently performed at adifferent illumination wavelength than fingerprint sensing. Further, itmay be appreciated that different wavelengths of light may be moreappropriate to image wet fingers, dry fingers, or gloved fingers. Assuch, multiple discrete flood illumination light emitting elements maybe preferable in certain embodiments.

Further, it may be appreciated that an optical imaging system such asdescribed herein may typically dispose light emitting and/or lightdetecting elements or pixels in a rectangular and/or array pattern,although this is not required of all embodiments. For example, in somecases, a circular deposition or distribution of light emitting and/orlight detecting elements of an optical imaging system such as describedherein may be more suitable.

Generally and broadly, FIGS. 5 and 6 depict simplified flow chartscorresponding to various ordered and/or unordered operations of methodsdescribed herein. It may be appreciated that these simplified examplesmay be modified in a variety of ways. In some examples, additional,alternative, or fewer operations than those depicted and described maybe possible.

FIG. 5 is a simplified flow chart depicting example operations of amethod of capturing an image of an object touching a display, such asdescribed herein. The method can be performed, in whole or in part, by aprocessor or circuitry of an electronic device such as described herein(see, e.g., FIGS. 1A, 2A-4B, and so on).

The method 500 includes operation 502 in which a touch to a display ofan electronic device is detected. The initial touch can be detectedusing any suitable sensor or combination of sensors including but notlimited to touch sensors and force sensors. Example touch sensorsinclude, but are not limited to: capacitive touch sensors; optical touchsensors; resistive touch sensors; acoustic touch sensors; and so on.Example force sensors include, but are not limited to: capacitive forcesensors; resistive force sensors; piezoelectric force sensors;strain-based force sensors; inductive force sensors; and so on.

Once a touch is detected at operation 502, the method 500 continues tooperation 504, in which a contact area of the detected touch isilluminated with shortwave infrared light. As noted with respect toother embodiments described herein, the illumination of the contactcentroid and/or contact area can be performed in any suitable mannerincluding, but not limited to: a specific/selected modulation of light;a specific/selected pattern (e.g., linear sweep, radial sweep, radialexpansion, and so on); and so on or any combination thereof.

The method 500 also includes operation 506 in which a fingerprint imageis captured by the optical imaging system of the electronic device. Asnoted with respect to other embodiments described herein, the operationof capturing an image of a fingerprint (or, more generally, an image ofan object in contact with the display at operation 502) can include oneor more filtering operations such as: spatial filtering (e.g.,point-source filtering, beam-forming, and so on); thresholding;deskewing; rotating; and so on.

FIG. 6 is a simplified flow chart depicting example operations of amethod of capturing an image of an object touching a display, such asdescribed herein. The method can be performed, in whole or in part, by aprocessor or circuitry of an electronic device such as described herein(see, e.g., FIGS. 1A, 2A-4B, and so on). The method 600 beings atoperation 602 in which a touch input is detected. Thereafter, atoperation 604, the contact area of the touch input is illuminated with aselected wavelength, such as 1450 nm or 1950 nm, or any suitableshortwave infrared wavelength. Finally, at operation 606, one or moreoptical properties of the contact area can be determined, including, butnot limited to: light absorption; light reflection; blood oxygenation;pulse rate; respiration rate; hydration; and so on.

One may appreciate that although many embodiments are disclosed above,that the operations and steps presented with respect to methods andtechniques described herein are meant as exemplary and accordingly arenot exhaustive. One may further appreciate that alternate step order or,fewer or additional operations, may be required or desired forparticular embodiments.

Although the disclosure above is described in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead can beapplied, alone or in various combinations, to one or more of the someembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments but is instead defined by the claims herein presented.

Further, the present disclosure recognizes that personal informationdata, including biometric data, in the present technology, can be usedto the benefit of users. For example, the use of biometricauthentication data can be used for convenient access to device featureswithout the use of passwords. In other examples, user biometric data iscollected for providing users with feedback about their health orfitness levels. Further, other uses for personal information data,including biometric data, that benefit the user are also contemplated bythe present disclosure.

The present disclosure further contemplates that the entitiesresponsible for the collection, analysis, disclosure, transfer, storage,or other use of such personal information data will comply withwell-established privacy policies and/or privacy practices. Inparticular, such entities should implement and consistently use privacypolicies and practices that are generally recognized as meeting orexceeding industry or governmental requirements for maintaining personalinformation data private and secure, including the use of dataencryption and security methods that meets or exceeds industry orgovernment standards. For example, personal information from usersshould be collected for legitimate and reasonable uses of the entity andnot shared or sold outside of those legitimate uses. Further, suchcollection should occur only after receiving the informed consent of theusers. Additionally, such entities would take any needed steps forsafeguarding and securing access to such personal information data andensuring that others with access to the personal information data adhereto their privacy policies and procedures. Further, such entities cansubject themselves to evaluation by third parties to certify theiradherence to widely accepted privacy policies and practices.

Despite the foregoing, the present disclosure also contemplatesembodiments in which users selectively block the use of, or access to,personal information data, including biometric data. That is, thepresent disclosure contemplates that hardware and/or software elementscan be provided to prevent or block access to such personal informationdata. For example, in the case of biometric authentication methods, thepresent technology can be configured to allow users to optionally bypassbiometric authentication steps by providing secure information such aspasswords, personal identification numbers, touch gestures, or otherauthentication methods, alone or in combination, known to those of skillin the art. In another example, users can select to remove, disable, orrestrict access to certain health-related applications collecting users'personal health or fitness data.

What is claimed is:
 1. An electronic device comprising: a cover definingan input surface; a display positioned below and adhered to the cover;and an infrared imaging system below the display and comprising: aninfrared light emitting element configured to emit shortwave infraredlight toward the input surface; and a light sensitive element configuredto receive, through the display, a reflection of the shortwave infraredlight; wherein the received reflection is used to construct a portion ofan image of a finger touching the input surface.
 2. The electronicdevice of claim 1, wherein the infrared light emitting element isconfigured to emit shortwave infrared light at a wavelength between 1400nm and 1500 nm.
 3. The electronic device of claim 2, wherein thewavelength is approximately 1450 nm.
 4. The electronic device of claim1, wherein the light sensitive element is optically isolated from theinfrared light emitting element.
 5. The electronic device of claim 1,wherein the received reflection is a surface reflection from the inputsurface.
 6. The electronic device of claim 1, wherein the lightsensitive element is disposed on, and formed with, a thin-filmtransistor layer of the display.
 7. The electronic device of claim 1,wherein the light sensitive element is separated from the infrared lightemitting element, at least in part, by an opaque mask layer.
 8. Theelectronic device of claim 1, further comprising a waveguide positionedbelow the display and optically coupled to the infrared light emittingelement.
 9. The electronic device of claim 8, wherein the infrared lightemitting element is disposed along an edge of the waveguide.
 10. Theelectronic device of claim 8, wherein the waveguide is configured toemit light between pixels of the display.
 11. A method of operating aninfrared imaging system positioned below a display of an electronicdevice, the method comprising: detecting, by a touch input sensor, acontact region of a touch input; illuminating the contact region with atleast one infrared light emitting element of the infrared imagingsystem; receiving one or more surface reflections of infrared light fromthe contact region; and assembling an image of an object initiating thetouch input from the one or more surface reflections.
 12. The method ofclaim 11, wherein the operation of illuminating the contact regioncomprises emitting shortwave infrared light at least partially throughinterpixel regions of the display.
 13. The method of claim 11, furthercomprising filtering the one or more received surface reflections with anarrow field of view filter.
 14. The method of claim 11, wherein the oneor more surface reflections correspond to features of a fingerprint of afinger providing the touch input.
 15. The method of claim 11, whereinthe operation of illuminating the contact region comprises emittingshortwave infrared light into a waveguide positioned at least partiallybelow the display.
 16. A method of imaging a transparent input surface,the method comprising: illuminating a substrate defining the transparentinput surface with shortwave infrared light; receiving one or moresurface shortwave infrared light reflections from the input surface atan array of light sensitive elements; and assembling an image of anobject in contact with the transparent input surface based on thereceived one or more surface shortwave infrared light reflections. 17.The method of claim 16, wherein the shortwave infrared light has awavelength greater than 1400 nm.
 18. The method of claim 16, wherein theshortwave infrared light has a wavelength greater than 1900 nm.
 19. Themethod of claim 16, wherein the received shortwave infrared lightreflections are filtered by a narrow field of view filter.
 20. Themethod of claim 16, wherein the image comprises a fingerprint.